1. Field of the Invention
The present invention relates to a magnetic recording and method of producing some medium suitable for high density recording. More particularly, it relates to a magnetic recording medium with improved erasing characteristics and productivity which comprises a magnetic layer having a thickness of not larger than 0.7 .mu.m.
2. Description of the Prior Arts
Conventionally, magnetic properties of a magnetic recording medium have been improved, for example, by orientating longer axis of acicular particles of magnetic powder in a direction along a longitudinal direction of the magnetic layer. However, in a magnetic recording medium utilizing magnetic components in the longitudinal direction of the magnetic layer, as the magnetic recording density increases, the strength of a demagnetic field in the magnetic layer also increases so that a decrease and rotation of the residual magnetization are caused, which makes it difficult to detect recorded signals. Therefore, the recording density has its own limit.
In a perpendicular magnetic recording system which utilizes a magnetic component perpendicular to the plane of the magnetic layer, the strength of the demagnetizing field decreases as the recording density increases, so that such recording system is recognized to be suitable for high density recording. For example, in the perpendicular magnetic recording system, hexagonal system ferrite powder, each particle of which has a platelet shape and magnetic easy axis in a direction perpendicular to said platelet plane, is used and contained in the magnetic layer so that planes of the platelets of the magnetic powder are orientated in parallel with the plane of the magnetic layer (cf. Japanese Patent Kokai Publication (unexamined) No. 209928/1985).
When a conventional magnetic head is used in combination with the perpendicular magnetic recording utilizing the magnetic component perpendicular to the plane of the magnetic layer, a perpendicular component of magnetization has a short range so that the erasing characteristics are deteriorated. To overcome such a drawback, it is well known to make the magnetic layer as thin as possible. However, the magnetic paint generally has poor electric conductivity and suffers from a large shearing stress when applied with a small thickness, whereby sores develop on the dried magnetic layer. Therefore, it is difficult to form a magnetic layer having a thickness as thin as possible over a long distance. This is the case, particularly when the hexagonal system ferrite magnetic powder is used, and since each particle of the powder has a smaller volume and poorer electric conductivity than conventionally used acicular magnetic powder, it is very difficult to form a magnetic layer having a thickness as thin as possible over a long distance.